The present invention relates to a mechanical optical switch of optical fiber direct driving type which is applied to optical communication and so forth.
A mechanical optical switch having a structure that an optical path is switched by directly driving an optical fiber is characterized by the simple structure, a little insertion loss, miniaturization, and low driving electric power. Switch structures of various types have been proposed in the past. FIG. 4 is a sectional view showing a conventional optical switch of optical fiber direct driving type. The conventional optical switch is composed of: a movable optical fiber 301 whose core line is fixed to a cylindrical tube 303 in a cantilever form, a magnetic body 310 having a desired magnetic characteristic and adhered to a surface of the movable optical fiber 301 in a vicinity of a tip thereof, a hollow solenoid coil 305 for inverting magnetic poles of both ends of the magnetic body 310; a pair of permanent magnets 307 which apply magnetic attraction to the magnetic body 310 in a direction vertical to an optical axis; two fixed optical fibers 302a, 302b fixed to a square hole formed within a columnar member 304; and a cylindrical sleeve 306 which aligns and holds the cylindrical tube 303 and the columnar member 304, and on which the solenoid coil 305 and the permanent magnets 307 are fixed respectively.
This switch operates as follows. The movable optical fiber 301 is magnetically attracted to one of the pair of permanent magnets 307 according to the magnetic poles of both the ends of the magnetic body 310. The tip of the movable optical fiber 301 optically combines with one of the two fixed optical fibers 302a and 302b in a corner of the square hole formed within the columnar member 304. The solenoid coil 305 is energized and a magnetic field along the optical axis is applied to the magnetic body 310 to invert the magnetic poles of the magnetic body 310. Then, the movable optical fiber 301 is attracted toward the other permanent magnet, thereby optically combining the other fixed optical fiber. Even when a current is not supplied, the magnetic body 310 can remain combined with one of the fixed optical fibers 302a and 302b because the magnetic body 310 is magnetically attracted to the permanent magnet 307, thereby obtaining a switching operation of latching type. Such a structure is disclosed in, for example, the Japanese Patent Publication No. Sho 64-11925.
However, the conventional mechanical optical switch of optical fiber direct driving type has one port on an input-side and two ports on an output-side (1.times.2 optical switch), which has the following problem. A plurality of 1.times.2 optical switches are necessary to form a 1.times.N mechanical optical switch (hereinafter referred to as "1.times.N optical switch") and a 2.times.2 mechanical optical switch (hereinafter referred to as "2.times.2 optical switch") respectively. For instance, in order to form a 1.times.4 optical switch and a 1.times.8 optical switch, generally three and seven 1.times.2 optical switches are connected in a branch-off structure as shown in FIG. 5(a) and 5(b) respectively. In order to form a 2.times.2 optical switch, it is necessary to connect four 1.times.2 optical switches in a branch-off and cross structure as shown in FIG. 5(c). Therefore, an object of the present invention is to solve the conventional problem mentioned above and to provide a compact 1.times.N optical switch and a compact 2.times.2 optical switch with a little loss by a simple element structure.